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For some, it is a vital stimulant and no day can begin without it. Others believe that drinking it has countless health benefits, citing studies that suggest its regular consumption could combat everything from heart disease to dementia. But coffee, which overtook tea as Britain’s favorite hot drink last year, doesn’t suit everyone. Reports suggest that even modest amounts can cause anxiety, palpitations, and sleepless nights.
The cause, of course, is caffeine, the stimulant that is one of the main components of coffee.
But why do people react badly? We spoke to coffee experts to find out, and they revealed surprising ways to maximize the benefits and enjoy the high while avoiding the downsides.
Coffee, which overtook tea as Britain’s favorite hot drink last year, doesn’t suit everyone.
In 2019, pop megastar Taylor Swift said L-theanine was her favorite supplement because it helps with her “stress and anxiety.”
SENSITIVITY TO COFFEE IS IN OUR GENES
Experts say that different reactions to coffee are found in our DNA. Caffeine can stay in the body for anywhere from 90 minutes to nine hours, depending on how quickly the liver (the organ that filters toxins from the blood) breaks it down.
Scientists have discovered that a specific gene, CYP1A2, controls how quickly the liver processes caffeine. About half the population has two copies of the CYP1A2 gene, meaning they burn caffeine quickly. About four in ten only have one copy of the gene, so coffee stays in their body longer. And about one in ten do not have the CYP1A2 gene. Their bodies can still break down caffeine, but it’s much harder for them, meaning the stimulant stays in the blood much longer, increasing the risk of sleep loss.
Some research suggests that people without the CYP1A2 gene may even develop high blood pressure as a result of drinking coffee. “Many people can break down coffee very quickly, which means they get that instant energy boost,” says Flick Lucas, a sports nutrition expert at Oxford Brookes, who is researching the effect of giving athletes caffeine before competitions.
‘But some don’t get that advantage and caffeine can stay in the body for up to nine hours, causing unwanted symptoms. Only in recent years have we begun to understand the important role that genetics plays in this effect.’
WHY TOO MUCH MAKES YOU FEEL TERRIBLE
Coffee (or rather caffeine) works by altering the flow of certain compounds and chemicals to the brain.
To sleep, the body produces a chemical called adenosine. When absorbed into the brain, it makes people feel tired and reduces heart rate. Throughout the day, the amount of adenosine in the body accumulates, so it is normal to start feeling sleepy in the afternoon.
But caffeine blocks the brain receptors through which adenosine is processed. “This makes you feel more alert and awake,” says Dr Duane Mellor, a dietitian at Aston University. Of course, this has its disadvantages. “You don’t want to be alert all the time with your heart racing,” adds Dr. Mellor.
“Adenosine also has a calming effect on the body, so if it is stopped for long periods of time, people may start to feel anxious.” Experts say that people who drink coffee regularly are less sensitive to its effects as their adenosine receptors develop resistance to caffeine.
Research also suggests that people who smoke are less affected by coffee because their adenosine receptors are already blunted by the effect of tobacco. However, studies suggest that genes are the main factor in how coffee affects the body.
HIGHLY STRUNG? BLAME THAT CHEAP INSTANT
Experts say that the type of bean used to prepare the coffee influences the amount of caffeine it contains. There are two coffee beans used by the vast majority of producers: Arabica and Robusta.
Arabica, which is the most expensive and popular bean, grows in the highest areas of the mountains.
It usually has a sweeter flavor. But robusta has 40 percent more caffeine. Most coffee shops use only Arabica beans. The same goes for more expensive instant coffee, such as Nescafé Gold Blend. However, cheaper instant types, such as Nescafé Original, contain a blend of Arabica and Robusta, meaning they can have a higher caffeine content. Even more crucial is how the coffee is prepared, according to experts.
At its most basic level, coffee is a combination of water and ground coffee beans, but brewing can make a big difference in the caffeine content. “The longer the contact time between the coffee and the water, the more caffeine the drink will have,” says Kurt Stewart, founder of Volcano Coffee Works in south London. ‘So American-style filtered coffee [where hot water is passed through the ground beans and a paper filter] It will never have much caffeine, so you can drink it all day.
‘The coffee with the highest caffeine content is cold brew, in which the ground beans are soaked in cold water for up to 24 hours. If you are sensitive to caffeine, I would avoid the cold brew. Espresso machines that you would normally buy at a coffee shop fall somewhere in the middle on the caffeine scale.
“It’s okay to drink in small amounts, but you don’t want to drink more than a few in a short space of time.”
ESPRESSO OVERDOSE? THIS IS WHAT TO DO
Scientists say there are steps people can take to counteract the undesirable effects of caffeine.
Studies show that drinking plenty of water (about a large glass for every coffee) can reduce the risk of jitters. This is because coffee is a diuretic, meaning it dehydrates the body. Experts say this can worsen the side effects of coffee, so they recommend drinking plenty of water if you’re feeling overcaffeinated.
Research also suggests that intense exercise (for example, running or cycling for 20 minutes) can reduce coffee cravings once started, as well as alleviate the risk of sleepless nights.
Experts maintain that this is probably due to the fact that exercise speeds up the metabolism of caffeine and breaks it down more quickly.
In recent years, there has been growing popularity for a supplement called L-theanine, which some social media influencers claim can eliminate jitters if taken before drinking coffee.
L-theanine is an amino acid found in black and green tea. In supplement form, it usually comes as an unflavored soluble powder (it can be mixed into a protein shake and some people also mix it directly into coffee). There have been several studies that suggest that it has an anxiolytic effect.
In 2019, pop megastar Taylor Swift said L-theanine was her favorite supplement because it helps with her “stress and anxiety.” Experts say there are suggestions that people can benefit from L-theanine. “Many people report that drinking tea, which often contains as much caffeine as coffee, does not cause anxiety,” says Dr. Mellor.
‘This may be because it contains L-theanine. The studies claiming it works as an anti-anxiety supplement have been too small to draw firm conclusions, but the science makes sense.’
DECAFF COULD HELP MORE THAN YOU THINK
One of the reasons researchers believe coffee may have health benefits is that it contains polyphenols, a group of compounds found in plants that are believed to have anti-inflammatory properties. Recent research also suggests that it contains a surprising amount of fiber, a crucial nutrient found primarily in fruits, vegetables and grains.
Professor Tim Spector, a British epidemiologist and creator of the nutrition app Zoe, says people who drink three to four cups of coffee a day get “considerable amounts of fibre.”
Research suggests that coffee contains about 1.5 grams of fiber, about the same as a glass of orange juice. The NHS recommends that people consume around 30 grams of fiber a day; However, studies suggest that less than a tenth of Britons get enough fibre.
Decaffeinated coffee is usually made by steeping fresh coffee beans in hot water. Since caffeine is water-soluble, this process removes about 97 percent of the stimulant, but the rest of the ingredients remain.
“Decaffeinated coffee still contains beneficial ingredients,” says Dr. Mellor.
‘And it may be able to give you an energy boost too. For many people, drinking coffee has more to do with habit than caffeine, it is a flavor they associate with starting the day. And you still feel that bitter taste with the decaf.
Experts say the demand for decaffeinated coffee is increasing.
“We have seen a clear increase in the number of customers requesting it,” says Kurt Stewart.
“Many people feel that they still feel the effect of coffee without the jitters; it’s a kind of placebo effect.”
And for those skeptical of this theory there is good news.
“Earlier this year, we tried a half and half coffee, a combination of caffeinated and decaffeinated,” adds Mr Stewart.
‘It was very popular, especially among those who are more sensitive to caffeine and those who want to drink it later in the day.
“We’re going to sell more and I think others might start doing the same too.”
…but be careful: too much caffeine can be deadly
It’s not just an urban myth: according to studies, it is possible to overdose on coffee.
In 2022, a 29-year-old British man died of cardiac arrest after accidentally consuming “up to 5g” of caffeine powder (not coffee).
Thomas Mansfield, a personal trainer who used caffeine to improve his energy levels while working out at the gym, drank seven times the recommended dose, according to research.
An Italian study, published in 2018, found 92 similar cases of caffeine overdose deaths in the medical literature. These deaths also involved consumption of more than 5 g of caffeine. A standard cup of coffee typically contains between 80 and 100 mg of caffeine, meaning you would need to drink 50 cups to overdose. But drinking more than 500 mg has been linked to uncomfortable side effects, such as heart palpitations and increased blood pressure.
Studies suggest that for people who don’t exercise, around 250 mg (about two and a half coffees) is an optimal amount of caffeine and is linked to desirable symptoms such as better concentration and even arousal.
However, experts say that for athletes, even a small coffee is enough to give them an advantage.
“We have discovered that a single shot of espresso can give athletes the boost they need,” says researcher Flick Lucas. “However, that’s only if you’re a rapid metabolizer of caffeine.”